Process of concentrating ores and flotation agents therefor



Patented Jan. 2, 1940 PATENT OFFICE PROCESS OF CONCENTRATING OBES AND FLOTATION AGENTS THEREFOR Anderson W. Ralston, William 0. Pool, and James Harwood, Chicago, 111., assignors to Armour and Company, Chicago, 11]., a corporation of Illinois No Drawing.-

60lalms.

l saturatedand unsaturated aliphatic hydrocarbons, said flotation agent advantageously being prepared by subjecting mixtures of aliphatic nitriles and hydrocarbons to hydrogenation.

In the co-pending application of Harwood and II Pool, flled April 28, 1937, Serial No. 139,611, there is described the use of mixtures of aliphatic hydrocarbons and aliphatic nitriles having from about three to ten carbon atoms as flotation agents in the froth flotation of ores. These mixtures of nitriles and hydrocarbons are advantageously made by subjecting relatively high molecular weight fatty acid nitriles, such as stearonitrile, to heat and pressure in the liquid phase, or to heat and a catalyst in the vapor a phase, and condensing a reaction mixture composedof lower molecular weight nitriles and hydrocarbons. Such methcdsflof preparing nitrilehydrocarbon mixtures are described and claimed in the Ralston, Pool and Harwood Patents 2,033,- 536 and 2,033,537.

The composition of the nitrile-hydrocarbon mixture will vary somewhat depending upon the kind of higher fatty acid nitriles, or mixtures thereof, used as a starting material, and the conditions during thepyrolysis. The predominating nitriles in such reaction mixtures ,will contain from three to ten carbon atoms, and the predominating hydrocarbons will contain from about flve to fourteen carbon atoms. Generally the respective quantitiesof individual nitriles present in the reaction mixture are about the same. There may, for example, be equal quantities of nitriles containing three, four and flve carbon atoms.-

Unsaturated nitriles and unsaturated hydro carbons are also present.

For example, when stearonitrile is heated at a cracking temperature under pressure the condensate is a pale yellow liquid containing a mixture of saturated and unsaturated nitriles asso- 50 ciated with liquid hydrocarbons. This condensate, when fractionated, yields the following fractions, assuming the starting mixture to be100 parts of condensate:

25 parts fraction 1 boiling range 40 C.-110 C. ll 25 parts fraction 2 boiling range 110 (IL-175 C.

. molecularweights.

Application November 1, 1937, Serial No. 172,284

25 parts fraction 3 boiling range 175 C.-220 C. 20 parts fraction 4 boiling range 220 C.2'75 C. 5 parts residue boiling range above 275 C.

These fractions consist of saturated and unsaturated nitriles and saturated and unsaturated 5 hydrocarbons falling within the boiling range indicated. The amount of saturated nitriles will roughly equal the amount of unsaturated nitriles, and there will be approximately equal quantities of saturated and unsaturated aliphatic hydrolo carbons.

We have now discovered that such nitrile-hydrocarbon mixtures can be hydrogenated to give mixtures of amines and hydrocarbons which mixu tures are markedly suitable as flotation agents in the froth flotation of ores. For example, a mixture of equal parts of proprionitrile, butyronitrile and valeronitrile can be hydrogenated to give a mixture of propyl amine, butyl amine and amyl amine. We wish to distinguish at this time, however, from the use as flotation agents of amine mixtures, or single amines, having relatively high In certain other co-pending applications in the name of Ralston and Pool there is described the froth flotation of ores in the presence of amines, such as octadecylamine having eighteen carbon atoms. We also wish to distinguish from those flotation processes which use substantially pure aliphatic amines having ten or more carbon. atoms. The amine mixtures which we obtain by the hydrogenation of nitrilehydrocarbon mixtures are all mixtures of relatively low molecular weight amines, both saturated and unsaturated, and hydrocarbons. The advantages present in our flotation agents are largely due to the fact that they are composed of mixtures of at least two or more amines and hydrocarbons.

In the past many different flotation agents have been proposed, such as oleic acid, fuel oil, xanthates and the like. It is recognized nowadays that best results are obtained when the ore to be separated by froth flotation is processed in the presence of substances which act as frothers and'substances which act as collectors. These collectors are believed to modify the interfacial tension .of the ore with respect to water. Our flotation agents can be looked upon as an intimate association of frothing agents and collectors. Undoubtedly, the hydrocarbons present act to to modify the surface tension relationships between ore and water, although there is also evidence that the amines we use have some surface tension modifying effect. The amines in our flotation mixtures also behave as frothing agents when used in conjunction with the hydrocarbons present. Mixtures of butylamine and heptylamine will alone act as froth flotation agents.

The action of our amine mixtures appears to be different from the action of the corresponding nitrile mixtures described in the aforesaid Harwood and Pool application 139,611 in that the amine mixtures of the present invention will concentrate by froth flotation a number of minerals and ores not concentrated as eflectively by the nitriles.

The aliphatic nitriles, namely those substances having the formula RCN wherein R is an alkyl group are also commonly described as alkyl cyanides. Propionitrile corresponds,'for example, to ethyl cyanide, butyronitrile is the sameas propyl cyanide, valeronitrile is the same as butylcyanide and yields pentyl amine on reduction. Because of the presence of unsaturated nitriles (cyanides) in our nitrile-hydrocarbon mixture, it will simplify identification of these materials if we refer to them as cyanides and this we do in the specific examples which follow. We shall now give examples of how our invention may be practised.

Example 1 of 84 per cent hydrogen and 16 per cent ammonia. The hydrogenation is continued for two hours in the presence of 2 per cent nickel catalyst. This nitrile-hydrocarbon mixture contains propyl cyanide, propenyl cyanide, butyl cyanide and butenyl cyanide, together with heptane, heptene, octane, octene, nonane and nonene. After hydrogenation the boiling point range is100 C. to 152 C. and the product consists of a solution of about equal parts by weight of butyl, butenyl, pentyl and pentenyl amines in about equal parts by weight of heptane, heptene, octane, octene, nonane and nonene, together with a. small amount of secondary amines. The amount of primary amines is approximately 24.9 per cent by weight and secondary amines 3.3 per cent by weight.

We have found that this amine-hydrocarbon mixture in the concentration of 400 parts per million gives essentially quantitative froth flotation of galena. When used for the flotation of an ore containing 1.5 per cent lead and 6.0 per cent zinc we use the equivalent of 2 pounds of amine-hydrocarbon mixture per ton of ore. The concentration of the amine-hydrocarbon mixture is approximately 400 parts per million. Under these conditions we obtain substantial froth flotation of the lead and after activation of zinc by the use of small amounts of copper sulfate an essentially quantitative recovery of zinc results.

Example 2 A mixture or" unsaturated and saturated nitriles and unsaturated and saturated hydrocarbons, boiling between 140 C. and 180 C., is subjected to hydrogenation under the conditions described in Example 1. The original nitrile-hydrocarbon mixture consists essentially of the following substances: Butyl cyanide, butenyl cyanide, pentyl cyanide, pentenyl cyanide, hexyl cyanide and hexenyl cyanide, together with nonane, decane, nonene and decene. After hydrogenation the amuse boiling point range is 120 C. to 220 C. and the product consists of a mixture of pentyl, pentenyl, hexyl, hexenyl, heptyl and heptenyl amines in about equal quantities, together with the above named saturated and unsaturated hydrocarbons and a small amount of secondary amines. This mixture in the concentration of 425 parts per million produces essentially quantitative froth flotation of galena. A concentration of 400 parts per million of this mixture produces essentially complete froth flotation of collophanite.

Example 3 A fraction of nitrile-hydrocarbons with a boiling point range of 180 C. to 200 C. is subjected to hydrogenating conditions as described under Example 1. The boiling point range of the hydrogenated product is 155 C. to 250 0., and .it consists of heptyl, heptenyl, octyl, and octenyl amines, together with decane, decene, undecane, undecene, dodecane and dodecene and a small amount of secondary amines. A concentration of 450 parts per million of this mixture gives essentially quantitative flotation of ga1ena. We also use it in a concentration of 450 parts per million for the flotation of rutile and chalcopyrite.

' The composition of the amine-hydrocarbon mixture can vary over rather wide limits depending upon the boiling point range of the nitrilehydrocarbon mixture which is subjected to hydrogenation. The product obtained from cracking high molecular weight nitriles may be fractionated so as to give a starting nitrile-hydrocarbon mixture of any boiling point range between the limits of the product; Approximately fifty per cent of the amines and hydrocarbons present will contain one double bond and the remainder will consist of saturated compounds. We believe where the double bond is present that it is in a terminal position. Our flotation agents will consist of two or more saturated or unsaturated amines in a mixture of saturated and um saturated hydrocarbons. It is quite difflcult to separate a saturated nitrile from an unsaturated nitrile of the same number of carbon atoms by distillation and it is also impossible to separate the nitriles from the hydrocarbons of the same boiling point range by distillation alone, so the mixtures which we hydrogenate will consist of at least the saturated and unsaturated nitriles in the presence of the hydrocarbons.

Our results indicate that the flotation agents of this invention can be used to concentrate by froth flotation the following minerals from ores containing the same.

Collophanite Chalcopyrite Pyroiusite Magnetite Malachite Franklinite Galena Apatite Rutile Zincite Chalcocite llmenite Pyrite In using our flotation agents we have proceeded in the accepted ways of this art. The ores are first ground and then mixed with water to form a pulp in the usual way. The flotation agent is then added and for experimental work the mixture subjected to froth flotation in a flotation cell. The mineral concentrate is skimmed off as a froth and collected, its composition and weight then determined.

So far as we are aware we are the first to describe mixtures of saturated and unsaturated aliphatic amines having from three to ten carbon atoms dissolved in straight-chain saturated and unsaturated hydrocarbons, and we broadly claim our invention with respect thereto. This mixture is superior for the flotation of both metallic and non-metallic ores because of the presence of both the saturated and unsaturated straightchain amines. In the presence of the olefins and parafiins the mixture performs the double function of preferentially wetting minerals to be floated'whereby its surface tension is so changed that the mineral will float, together with imparting irothing characteristics to the pulp. Consequently, we do not need any additional frothing agent, but our invention is not to be construed so narrowly as toexclude the addition of further frothing agents. These flotation agents described have a decided advantage over the pure compounds now used because of the cumulative efiect of the various components herein described and also because of their cheapness and. availability.

Having thus described our invention, what we claim is:

1. The process of concentrating ores which comprises subjecting the ore to froth flotation separation in the presence of a mixture of saturated and unsaturated aliphatic amines having from three to ten carbon atoms and saturated and unsaturated aliphatic straight-chain hydrocarbons.

2. In the froth flotation of ores the step comcomprises subjecting an aqueous pulp of the ore' to froth flotation in the presence of a flotation agent comprising a mixture of aliphatic amines containing from three to ten carbon atoms in substantial amounts, together with straightchain aliphatic hydrocarbons.

4. A flotation agent comprising an aliphatic hydrocarbon solution of saturated and unsaturated aliphatic amines having from three to ten carbon atoms.

5. A flotation agent comprising an aliphatic hydrocarbon solution of at least one unsaturated aliphatic amine having from three to ten carbon atoms.

6. A flotation agent comprising a hydrocarbon solution of at least two aliphatic amines chosen from the group consisting of butyl, butenyl, pentyl, pentenyl; hexyl, hexenyl, heptyl and heptenyl amines, one of said chosen amines bein unsaturated.

' ANDERSON W. RALSTON.

WILLIAM O. POOL. JAMES HARWOOD. 

